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Old 24th November 2010, 01:09 PM   #1
00940 is online now 00940  Belgium
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Default How much would a cathode follower drift ?

In the following schematic, what kind voltage of drift should I expect at the output over time ?

The output would go into an output transformer that can't stand more than a few mA of DC current and I wonder if I should implement a DC servo (probably a copy of SY's Heretical).

Thanks
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Old 24th November 2010, 01:42 PM   #2
DF96 is offline DF96  England
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It will drift a huge amount. This is because for DC purposes the CF is not a CF at all but common-cathode with cathode bias. Without a DC servo there is little chance of the output ever being near 0V.

A DC CF would be better, but still not good enough if you want accuracy to mA levels.
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Old 24th November 2010, 04:23 PM   #3
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Thanks.

A servo is no big deal after all... it avoids the nightmare of matching a parafeed cap to the output xformer for best frequency response.
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